What is in it
Lemon juice’s main polyphenols are two flavanones, hesperidin and eriocitrin, both attached to sugars (Phenol-Explorer, n.d.).
Before these flavanones can be absorbed, the sugar has to be removed, and in the colon this is done by gut bacteria. In a study of 16 healthy adults given a single dose of each, eriocitrin from a lemon extract reached the blood faster and at much higher levels than the same amount of hesperidin: the peak came at about 6 hours rather than 8, and total exposure was roughly 16 times higher. People varied widely in how much they absorbed (Ávila-Gálvez et al., 2021). The authors suggest that eriocitrin, which dissolves more easily in water, is easier for gut bacteria to work on, but they did not test this.
In the recipes on this site, lemon is used in small amounts, a squeeze in the NO-Boost Smoothie and on the Phytonutrient Plate, so it adds only a little to their polyphenol content.
Polyphenols at a glance
These figures come from the Phenol-Explorer database and are given in mg per 100 g of the fresh food (Neveu et al., 2010; Phenol-Explorer, n.d.). The database records how each value was measured, and the methods are not interchangeable: chromatography identifies and measures individual compounds, some values are measured after the compounds have been broken down chemically (hydrolysis), and the Folin assay gives a single figure for total phenolic content.
Reading these figures. Lemon juice is dominated by two flavanones, hesperidin and eriocitrin, which are attached to sugars. Hesperidin averages about 17.8 mg per 100 ml, but ranges from 0 to 43.5 mg across 17 samples from 5 studies. The whole-lemon values are measured after hydrolysis, which removes the sugars, so eriodictyol and hesperetin there are the same compounds as eriocitrin and hesperidin in the juice, without their sugars. The two sets of figures should not be added together.
A squeeze of lemon is a small amount, so it adds only a little to the polyphenol content of a recipe. Vitamin C is not a polyphenol, so it is not included here.
What the evidence tells us
Well supported
None of the lemon findings we have read so far reaches this label. None of the human studies we have read in full used real lemon or lemon juice.
Promising
Iron absorption. Juices rich in vitamin C increased how much iron 234 women absorbed from a rice meal, and absorption rose with the vitamin C content of the fruit or juice. The “lemon juice” in this study was made in the laboratory by adding citric acid to orange juice, and it increased iron absorption more than orange juice alone (Ballot et al., 1987). The study did not test real lemon, and the authors note that most of the fruits tested would be expected to have only a small effect. No funding statement was included.
Blood sugar. In a 12-week crossover trial in 30 adults with raised blood sugar, a supplement made mostly of eriocitrin (200 mg a day) lowered fasting glucose by 5% and raised the gut hormone GLP-1 by 17% compared with the start, while glucose rose 4% on placebo. Markers of inflammation also fell. HbA1c, blood fats, blood pressure and weight did not change. The trial was funded by the company that makes the supplement, and some figures differ between the abstract and the results, so it needs repeating independently (Cesar et al., 2022).
Plausible pathway
Gut bacteria and absorption. Gut bacteria are needed to release hesperetin from hesperidin, and people’s stool bacteria differ in how well they do this (Amaretti et al., 2015). This may help explain why people vary so much in how much lemon flavanone they absorb (Ávila-Gálvez et al., 2021).
What we do not know
The absorption study gave a single dose of a lemon extract providing 260 mg of eriocitrin, far more than a squeeze of juice, and it compared it with an orange extract that was almost pure hesperidin, a limitation the authors acknowledge. We have not yet checked that paper’s funding and conflict of interest statements (Ávila-Gálvez et al., 2021). We have not been able to read a trial of daily lemon and walking on blood pressure.
References
Ávila-Gálvez, M. Á., Giménez-Bastida, J. A., González-Sarriás, A., & Espín, J. C. (2021). New insights into the metabolism of the flavanones eriocitrin and hesperidin: A comparative human pharmacokinetic study. Antioxidants, 10(3), Article 435. https://doi.org/10.3390/antiox10030435
Amaretti, A., Raimondi, S., Leonardi, A., Quartieri, A., & Rossi, M. (2015). Hydrolysis of the rutinose-conjugates flavonoids rutin and hesperidin by the gut microbiota and bifidobacteria. Nutrients, 7(4), 2788–2800. https://doi.org/10.3390/nu7042788
Ballot, D., Baynes, R. D., Bothwell, T. H., Gillooly, M., Macfarlane, B. J., MacPhail, A. P., Lyons, G., Derman, D. P., Bezwoda, W. R., Torrance, J. D., Bothwell, J. E., & Mayet, F. (1987). The effects of fruit juices and fruits on the absorption of iron from a rice meal. British Journal of Nutrition, 57(3), 331–343. https://doi.org/10.1079/BJN19870041
Cesar, T. B., Ramos, F. M. M., & Ribeiro, C. B. (2022). Nutraceutical eriocitrin (Eriomin) reduces hyperglycemia by increasing glucagon-like peptide 1 and downregulates systemic inflammation: A crossover-randomized clinical trial. Journal of Medicinal Food, 25(11), 1050–1058. https://doi.org/10.1089/jmf.2021.0181
Neveu, V., Perez-Jiménez, J., Vos, F., Crespy, V., du Chaffaut, L., Mennen, L., Knox, C., Eisner, R., Cruz, J., Wishart, D., & Scalbert, A. (2010). Phenol-Explorer: An online comprehensive database on polyphenol contents in foods. Database, 2010, Article bap024. https://doi.org/10.1093/database/bap024
Phenol-Explorer. (n.d.). Showing all polyphenols found in lemon (Version 3.6) [Data set]. Retrieved October 18, 2026, from http://phenol-explorer.eu/contents/food/16
Phenol-Explorer. (n.d.). Showing all polyphenols found in lemon, pure juice (Version 3.6) [Data set]. Retrieved October 18, 2026, from http://phenol-explorer.eu/contents/food/17
